This invention relates to a process for the production of (xe2x88x92) 3,4-divanillyl tetrahydrofuran. More particularly, this invention relates to an improved process for the isolation of (xe2x88x92) secoisolariciresinol from the heart wood and roots of Taxus wallichiana and conversion of (xe2x88x92) secoisolariciresinol of formula (1) into its semisynthetic analog (xe2x88x92) 3,4-divanillyl tetrahydrofuran of formula (2). 
(xe2x88x92) secoisolariciresinol is a known molecule and it has previously been isolated from the heartwood of T. wallichiana but it has never been isolated from, the roots of T. wallichiana. According to a prior art process, (xe2x88x92) secoisolariciresinol has been isolated from the heartwood of T. wallichiana consists of extracting the powdered heartwood with cold methanol and concentrating the methanol to get methanol extract, treating the methanol extract with hot petroleum-ether to remove waxes and subjecting the dewaxed material to counter current distribution process between equal volumes of benzene, ethyl acetate, water, methanol yielding three main fractions, subjecting the desired fraction containing (xe2x88x92) secoisolariciresinol to column chromatography and isolating (xe2x88x92) secoisolariciresinol from the column by eluting with benzene acetone as eluent with a yield of 0.1% (Taxiresinol, a new lignan in the heartwood of Taxus baccata [R. B. Mujumdar, R. Srinivasan and K. Venkataraman, Indian J. Chem 10, 677-680 (1972)].
The process described above for the isolation of (xe2x88x92) secoisolariciresinol from T. wallichina suffers from several disadvantages which include, extra step of defatting with petroleum ether, use of benzene (which is carcinogenic) as a solvent both in the counter current distribution process and also as a eluent during isolating from the column and the use-of column chromatography which makes the process tedious, time consuming and required extra volumes of solvents.
According to another prior art process, the preparation of (xe2x88x92) 3,4-divanillyl tetrahydrofuran of formula (2) from (xe2x88x92) secoisolariciresinol of formula (1) involves the treatment of (xe2x88x92) secoisolariciresinol in an acetone solution with perchloric acid. The drawback of the process includes that the epoxide of formula (2) thus formed is unstable in acidic solution and it gets partly decomposed to the starting material i.e. (xe2x88x92) secoisolariciresinol of formula (I).
The plant Taxus wallichiana is an important plant from the medicinal point of view as it contains the anticancer compound paclitaxel (=taxol(copyright)) in it. Paclitaxel, a highly oxygenated diterpenoid molecule and a potent anticancer drug for the treatments of ovarian and breast cancers, was first isolated from Taxus brevifolia. Thereafter, it has also been isolated from the Himalayan yew Taxus wallichiana. We have been working on different parts-stem bark, needles, heartwood, roots and seeds of T. wallichiana as a part of our systematic investigation on the plant for the isolation of paclitaxel, its important analogs, precursors and other biologically active molecules. During the course of this investigation, we have been able to isolate an important molecule (xe2x88x92) secoisolariciresinol of formula (1) from the heartwood as well as roots of this plant with high yields.
Recent findings have established that (xe2x88x92) secoisolariciresinol possesses significant aromatase inhibition property. Aromatase is a key enzyme in steroid hormone metabolism. It mediates the conversion of androgens into estrogens. Aromatase is of considerable therapeutic interest since estrogen production has been associated with endometrial and breast cancers. Aromatase inhibitors are used in treating estrogen dependent breast cancers.
(xe2x88x92) secoisolariciresinol is also capable of reducing the binding of 3H-labelled 5a-dihydro testosterone (DHT) to human sex hormone binding globulin (SHBG) and thereby reduces the chance of growth of prostate cancer. However, the semisynthetic analog (xe2x88x92) 3,4-divanillyl tetrahydrofuran prepared from (xe2x88x92) secoisolariciresinol by the process of the invention is more active in reducing the bindina of 3H-labelled 5a-dihydro testosterone (DHT) to human sex hormone binding globulin (SHBG). Thus (xe2x88x92) 3,4-divanillyl tetrahydrofuran is more active than (xe2x88x92) secoisolariciresinol in reducing the chance of growth of prostate cancers in human.
The object of the present invention is to develop an improved process for isolation of (xe2x88x92) secoisolariciresinol from the heartwood and roots of T. wallichiana with high yields.
Another object of the present invention is to develop a processing technology for the isolation of (xe2x88x92) secoisolariciresinol from the heartwood and roots of T. wallichiana which does not use any chromatographic separation for its isolation.
Yet another object of the present invention is to avoid the use of carcinogenic solvent benzene for isolation of (xe2x88x92) secoisolariciresinol.
Still another object of the present invention is to convert (xe2x88x92)secoisolariciresinol of formula (1) into its more active semisynthetic analog (xe2x88x92) 3,4divanillyl tetrahydrofuran of formula (2) under neutral condition.
Yet another object of the present invention is to convert (xe2x88x92) secoisolariciresinol into (xe2x88x92) 3,4-divanillyl tetrahydrofuran with high yields.
In order to overcome the drawbacks of the prior art processes, we have developed a simple and practical process for production of (xe2x88x92) 3,4,-divanillyl tetrahydrofuran of formula (2) 
comprising (a) extracting the pulverized heartwood/roots of T. wallichiana with alcohol at ambient temperature and concentrating the solvent furnished an alcoholic extract, (b) treating the alcoholic extract with water and extracting with a chlorinated solvent exhaustively (c) concentrating the chlorinated solvent to a residue and treating the residue with aqueous solution of a base and extracting the alkaline layer with an organic solvent (d) neutralizing the aqueous alkaline solution with mineral acid and extracting with an organic solvent (e) concentrating the organic solvent to a residue and crystallizing it from a suitable organic solvent or mixture of such solvents to get (xe2x88x92) secoisolariciresiniol of formula (1), 
(f) dissolving the isolated (xe2x88x92) secoisolariciresinol in an organic solvent and reacting it with triphenyl phosphine halide at 0-80xc2x0 C. for 1-10 hours and (g) isolating (xe2x88x92) 3,4-divanillyl tetrahydrofuran of formula (2) by column chromatography.
Accordingly the present invention relates to a process for the preparation of (xe2x88x92) 3,4-divanillyl tetrahydrofuran of formula (2), said process comprising (f) dissolving the isolated (xe2x88x92) secoisolariciresinol in an organic solvent, reacting it with triphenyl phosphine halide at 0-80xc2x0 C. for 1-10 hours and (g) isolating (xe2x88x92) 3,4-divanillyl tetrahydrofuran of formula (2) by column chromatography.
In one embodiment of the present invention the alcohol used in step (a) is an alkanol selected from the group consisting of methanol and ethanol.
In another embodiment of the invention, the chlorinated solvent in step (b) is selected from the group consisting of chloroform and dichloromethane.
In yet another embodiment of the invention, the base used in step (c) is selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide.
In a further embodiment of the present invention, the organic solvent used in step (c) is selected from the group consisting of toluene chloroform, dichloromethane and ethyl acetate.
In yet another embodiment of the present invention, the mineral acid in step (d) is selected from the group consisting of hydrochloric acid and sulphuric acid.
In yet another embodiment of the invention, the suitable organic solvent or mixtures of such solvents used in step (e) is selected from the group consisting of acetone, and mixtures of acetone-petroleum ether, acetone-hexane, ethyl acetate-pet.ether and ethylacetate-hexane.
In another embodiment of the invention, the organic solvent used in step (f) for dissolving (xe2x88x92) secoisolariciresinol, is selected from the group consisting of acetonitrile, methanol, tetrahydrofuran, chloroform and dichloromethane.
In a yet another embodiment of the present invention, the triphenyl phosphine halide used in step (f) is selected from a group consisting of triphenyl phosphine bromide and triphenylphosphine chloride.
In a further embodiment of the present invention, the column chromatography used in step (g) is selected from a group consisting of silica gel, florosil, alumina and celite.
The process of the invention for the isolation of (xe2x88x92) secoisolariciresinol from the heartwood and roots of T. wallichiana does not use column chromatography. The improved isolation process comprises (a) extracting the pulverized heartwoods/roots of T. wallichiana with an alcohol at ambient temperature and concentrating the solvent to obtain an alcoholic extract, (b) treating the alcoholic extract with water and extracting it with chlorinated solvents exhaustively (c) concentrating the chlorinated solvent to a residue and treating the resultant residue with aqueous solution of a base and extracting the alkaline layer with an organic solvent (d) neutralizing the alkaline solution with mineral acid and extracting with an organic solvent, (e) concentrating the organic solvent to a residue and crystallizing it from a suitable organic solvent or mixtures of such solvents to get (xe2x88x92) secoisolariciresinol of formula (1).
The isolated (xe2x88x92) secoisolariciresinol of formula (1) is converted into (xe2x88x92) 3,4-divanillyl tetrahydrofuran of formula (2) by (f) dissolving the isolated (xe2x88x92) secoisolariciresinol in an organic solvent, reacting it with triphenyl phosphine halide at 0-80xc2x0 C. for 1-10 hours and (g) isolating (xe2x88x92) 3,4-divanillyl tetrahydrofuran of formula (2) by column chromatography.
The alcohol used in step (a) can be an alkanol such as methanol and ethanol. The chlorinated solvent in step (b) is selected from the group consisting of chloroform and dichloromethane. The base used in step (c) is selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide.
The organic solvent used in step (c) is selected from the group consisting of toluene, chloroform, dichloromethane, ethyl acetate. The mineral acid in step (d) is selected from the group consisting of hydrochloric acid, sulphuric acid. The suitable organic solvent or mixtures of such solvents used in step (e) comprises acetone, and mixtures of acetone-petroleum ether acetone-hexane, ethyl acetate-pet.ether, ethylacetate-hexane or any mixture thereof.
The organic solvent used in step (f) for dissolving (xe2x88x92) secoisolariciresinol, is selected from the group consisting of acetonitrile, methanol, tetrahydrofuran, chloroform, dichloromethane. The triphenyl phosphine halide used in step (f) is selected from a group consisting of triphenyl phosphine bromide, triphenylphosphine chloride.
The column chromatography used in step (g) is selected from a group consisting of silica gel, florosil, alumina, celite.